Given their arrogance, pomposity and habitual absurdities, it is hard not to feel a certain satisfaction with the comeuppance that Brexit has delivered to the unaccountable European Union bureaucrats in Brussels.

Nonetheless, we would do well to refrain from smug condescension. Unity is not easy. What began in 1951 as a six-member European Coal and Steel Community was grounded in a larger conception of a united Europe born from the ashes of World War II. Seven decades into the postwar era, Britain wants out and the E.U. is facing an existential crisis.

Yet where were we Americans seven decades into our great experiment in continental confederation, our "more perfect union" contracted under the Constitution of 1787? At Fort Sumter.

The failure of our federal idea gave us civil war and 600,000 dead. And we had the advantage of a common language, common heritage and common memory of heroic revolutionary struggle against a common (British) foe. Europe had none of this. The European project tries to forge the union of dozens of disparate peoples, ethnicities, languages and cultures, amid the searing memories of the two most destructive wars in history fought among and against each other.

The result is the E.U., a great idea badly executed. The founding motive was obvious and noble: to reconcile the combatants of World War II, most especially France and Germany, and create conditions that would ensure there could be no repetition. Onto that was appended the more utopian vision of a continental superstate that would once and for all transcend parochial nationalism.

That vision blew up with Brexit on June 23. But we mustn't underestimate the significance, and improbability, of the project's more narrow, but still singular, achievement - peace. It has given Europe the most extended period of internal tranquility since the Roman Empire. (In conjunction, of course, with NATO, which provided Europe with its American umbrella against external threat.)

Not only is there no armed conflict among European states. The very idea is inconceivable. (Fighting among the various nations has been subcontracted to soccer hooligans.) This on a continent where war had been the norm for a millennium.

Give the E.U. its due. Despite its comical faux-national paraphernalia of flag, anthem and useless parliament, it has championed and advanced a transnational idea that has helped curb the nationalist excesses that culminated in two world wars.

Advanced not quite enough, however. Certainly not enough to support its disdainful, often dismissive, treatment of residual nationalisms and their democratic expressions. Despite numerous objections by referendums and parliaments, which it routinely either ignored or circumvented, the E.U. continued its relentless drive for more centralization, more regulation and thus more power for its unelected self.

Such high-handed overriding of popular sentiment could go on only so long. Until June 23, 2016, to be precise.

To be sure, popular sentiment was rather narrowly divided. The most prominent disparity in the British vote was generational. The young, having grown up in the new Europe, are more comfortable with its cosmopolitanism and have come to expect open borders, open commerce and open movement of people. They voted overwhelmingly - by 3 to 1 - to Remain. Leave was mainly the position of an older generation no longer willing to tolerate European assaults on British autonomy and sovereignty.

Understandably so. Here is Britain, inventor of the liberal idea and home to the mother of parliaments, being instructed by a bunch of pastry-eating Brussels bureaucrats on everything from the proper size of pomegranates to the human rights of terrorists.

Widely mentioned, and resented, was the immigration directive to admit other E.U. citizens near-automatically. But what pushed the Leave side over the top was less policy than primacy. Who runs Britain? Amazingly, about half of the laws and regulations that govern British life today come not from Westminster but from Brussels.

Brexit was an assertion of national sovereignty and an attempt, in one fell swoop, to recover it.

There is much to admire in that impulse. But at what cost? Among its casualties may be not just the European project (other exit referendums are already being proposed) but possibly the United Kingdom itself. The Scots are already talking about another vote for independence. And Northern Ireland, which voted to remain in the E.U., might well seek to unite with the Republic.

Talk about a great idea executed badly. In seeking a newly sovereign United Kingdom, the Brits might well find themselves having produced a little England.